For changes, SMA1 (SMB2) has a ton of life-up items tossed around, a new boss, and the "Yoshi Challenge" where you need to find Yoshi eggs and bring them to the end of the stage without dying. SMA2 (SMW) doesn't have much - you can play as SMB2 Luigi and there are 5 dragon coins on each level, plus it's easier to get colored yoshis. SMA3 (SMW2) has 6 all-new levels at the end of the game, and SMA4 (SMB3) has e-reader support, allowing for some minor level changes and a bunch of all-new level. Most of the interesting changes requires Japanese-imported cards, though.